

" Geology tells us of the successive i-evolutions and changes in the 

 crust of the eai-th. Organic changes are our surest guides in making 

 out this history, but they form only a part of our evidence, and the 

 great physical groups of deposits, however rude and mechanical, are 

 historical monuments of perhaps equal importance in obtaining any 

 true and intelligible history of the past ages of the earth ; and after 

 we have descended through a certain nmnber of stages, they become, 

 indeed, our only monuments and indexes of past events." — Sedgwick. 



Printed by BEEVE, BROTHERS, King WiUiam Street, Strand. 



